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Genetic modification is the manipulation of an organism's genes to introduce particular traits. All methods of breeding modify the genes, but the technique that is usually implied by the term "genetic modification," and that attracts the greatest deal of controversy, is DNA recombination[citation needed] - introducing genes from one species into another.

There are several methods to obtain organisms with more favourable genetic make-up. All of these occur in nature to some degree; even DNA recombination can happen naturally, through viruses. All important modern crops have been extensively modified by human action.

Selective breeding is the oldest method, dating back to the beginnings of agriculture, and uses the same fundamental mechanism as natural evolution. The primary difference is that people select for desired traits in individuals, rather than the natural events determining survival and reproductive opportunity (natural selection). Most commercially important plants and animals are a result of centuries of this process; cows were bred from the now-extinct aurochs, chickens from the red jungle fowl, and pigs from wild boars.

Hybridisation involves crossing two highly dissimilar strains of an organism with each other. Because most detrimental alleles are recessive, and are unlikely to occur in both strains, this results in organisms that suffer from very few genetic defects (sometimes called "heterosis" or "hybrid vigour"). Examples include the sunflower and "broccoflower" (broccoli x cauliflower) for plants, and the mule (mare and jackass) for animals. Hybrids are sometimes sterile, especially within the animal kingdom.

Doubled haploidy involves the action of the chemical colchicine, which interferes with reduction division and causes gametes to contain two sets of chromosomes rather than one. This results in an organism in which all traits are homozygous. This crude modification can lead to a number of important effects, such as making a plant fertile after wide crossing.

Mutation breeding involves subjecting organisms (usually plants) to chemical mutagens or ionising radiation. This increases the rate of mutation, and therefore the chance of finding new interesting traits. Naturally, it also increases the chance of fucking up everything and killing the plant, but you can't have your cake and eat it too. Over 2500 registered varieties have been obtained through radiation breeding.[1]

DNA recombination, the most recent of the bunch, is basically genetic copy-paste; the genetic code of an organism is directly modified by inserting foreign genes into its DNA, often through a specially prepared virus or bacterial plasmid(The CRISPR method may be used too). This is the most precise and powerful method of genetic manipulation, and also the only one that attracts substantial controversy. Examples of this are E. coli strains with genes to make insulin. In defiance of Common sense, this happens in nature all the time, so the appeal to nature argument fails.

Genetic modification has a wide range of applications. The most common genetically modified crops are designed to resist pests,[2] herbicides,[3] and plant viruses.[4] These engineered traits can produce higher yields (due to decreased pressure from weeds/insects),[5][6][7][8][9] reduce the amount of carcinogenic mycotoxins present in the food,[10] reduce insecticide use (and insecticide poisoning cases),[11] encourage beneficial bugs,[12] and supports the use of no-till agriculture, which reduces runoff[13] and soil erosion.[14]

Genetic engineering holds incredible potential for the future as well. Crops with increased yield, improved nutrition (like Golden Rice),[15] longer shelf lives (like the nonbrowning Arctic Apple),[16] disease resistance, fungus resistance, and more are currently being developed and tested. There are also a few failed projects, such as the Flavr Savr tomato[17] and Guelph University's Enviropig.[18]

Genetic engineering can also be used for non-food crops, such as poplars grown for wood, cotton, or potatoes grown for starch. The Amflora potato, which produces amylose-free starch particularly suitable for paper production and other industrial uses, was a notable case.

Another very important area is the use of bacteria or fungi (yeast) genetically engineered to produce a specific protein. This method is used to manufacture several therapeutic proteins with important medical uses, such as insulin and human growth hormone. In the future, these proteins may be made even cheaper by genetically engineering goats, pigs, or cows to produce them in their milk.[19]

Other uses of genetic modification include the creation of a new lithium-ion battery,[20] glow-in-the-dark monkeys,[21] and even creating superheroesDo You Believe That? or, if otherwise inclined, your very own Legion of Terror.Do You Believe That?

Genetic modification plays straight into what Isaac Asimov called "The Frankenstein Complex," where there is an irrational fear of those who "play God" by mucking with nature. Indeed, many opponents refer to GM food as "Frankenfood."[22]

Opposition to GM foods is rife with bad argumentation. The shill gambit is especially common, with the company Monsanto in particular as such a common bogeyman that Brian Dunning of Skepticblog has coined the term "argumentum ad monsantium" to refer to the use of the gambit in this context. The appeal to nature is often invoked as well. Another common claim from opponents is that the consumption of GM foods can cause cancer or birth defects, but there is no evidence to support this claim.

The prospect of human genetic engineering has also been extremely controversial, less for health reasons and more out of ethical concerns. The practice does not now exist, but prenatal screening now allows parents to test a fetus or zygote for gender or disease. Critics point to a slippery slope, arguing that if parents can choose to only bear male children or rule out any children with a heightened risk of cancer, then it's likely that when technology allows they will also choose to bear only exceptionally intelligent children or those with other commonly-desired traits, such as blue eyes. As a side effect of this, genetic variation could be reduced and humankind as a whole could become less resistant to disease. The desirable traits could also become a visible indicator of social class and contribute to prejudice and lower social mobility for people who lack them. However, on the others hand, specific genetic traits which make people more resistant to disease could be dynamically introduced into the population. Also, human genetic engineering could put an end to some people being born "luckier" than other, with each person getting a genetic configuration which would enable them to be successful in life, rather than the current status where some people are born with lower intelligence or lack of certain senses. However, since the standards that decide what is good and what is bad are not universal and have no objective basis, there needs to be a species-wide discussion to decide what they will be. Otherwise, this technology could be abused, especially in the hands of authoritarian regimes with no respect for human rights.

Because of potential problems with social mobility some have referenced the likely introduction of gene therapy into medical practice as giving governments even more reason to pursue universal health care policies if they have not already done so.[23].

In 2017, scientists managed to save a child who was suffering from junctional epidermolysis bullosa, a deadly genetic disease. The feat was done by replacing 80% of his epidermis with a genetically engineered and cell culture grown replacement.[25][26]

A surprisingly large amount of science fiction deals with human genetic engineering in one form or another.

Movies such as the 1997 science fiction thriller Gattaca have conceived of a world rigidly stratified by genetic code, where the wealthy bear superhumans and a person's opportunities for advancement - as well as the concurrent creativity and growth of society - is limited to what's dictated by their genes. Surprisingly, this raises a good question that is as yet unanswered: does the diversity brought about by genetic variation and flaws outweigh the personal costs of parents' private tragedy?